The present invention relates to a latex-saturated or polymer-reinforced paper. More particularly, the present invention relates to a latex-saturated or polymer-reinforced paper which may be used in a clean room environment.
Clean room documentation paper may be used to record the results of various steps in a clean room manufacturing process. It also may be used as copier paper and as computer forms. Clean room paper also may be used in roll form to print equipment operation manuals and for such ancillary uses as notebooks and memo pads. The type of paper used primarily for recording is 8.5 inch by 11 inch cut sheets. These standard sheets normally are printed by the user (although printing may be contracted). Most forms use either different colors of ink or papers of different colors to identify different forms. The primary attribute of any paper used in a clean room is that the paper must generate a low number of particulates into the environment. Other product attributes include copyability, writability, printability, durability, and price.
Paper used in a clean room is, of course, a potential source of contamination by the emission of particles. Such emissions are believe to originate from either particles deposited on the surfaces of the paper during its manufacture, handling, and storage, or from the mechanical disintegration of the paper itself. Thus, particles may be generated by disintegration of the paper structure under high stresses that accompany folding, creasing, abrading, or shredding. Such disintegration represents an unavoidable source of particle emissions which is a characteristic of all papers, although some paper structures are less vulnerable to disintegration and, as a consequence, less likely to shed particles under normal usage.
Standard papers used for documentation, such as bond papers, typically generate 5,000 to 40,000 particles, 0.5 micrometers or larger, per linear inch when crumpled or torn. Polymer-reinforced papers (often referred to herein as saturated papers or latex-saturated papers) typically have low particle generation from tearing actions. The reinforcement of paper by polymer impregnation, of course, is a long-established practice. The polymer employed typically is a synthetic material, and the paper can consist solely of cellulosic fibers or of a mixture of cellulosic and noncellulosic fibers. Polymer reinforcement is employed to improve one or more of such properties as dimensional stability, resistance to chemical and environmental degradation, resistance to tearing, embossability, resiliency, conformability, moisture and vapor transmission, and abrasion resistance, among others. Papers containing only synthetic thermoplastic fibers, such as Tyvek.RTM., are very difficult to tear and generate very low levels of particulates. Such papers, however, typically cannot be copied and are relatively expensive.
Accordingly, there is a need for a paper which is suitable for use in a clean room, but which is durable, less expensive than synthetic papers, and is capable of being copied and/or printed on.